As the infrastructure of modern nations continues to age, many rehabilitation methods have been developed to minimize the need to fully replace the existing infrastructure. Such methods are usually cost effective options that decrease any disruption in traffic or lifestyle caused by replacing existing structures. For example, the cured-in-place pipelining method of pipe rehabilitation has been known as a viable option for infrastructure repair or rehabilitation. The method involves impregnating a fabric liner with a resin capable of curing and hardening, placing the liner against the interior of a pipe to be repaired, applying fluid pressure to the liner, and allowing the resin to cure and harden. The result is an existing pipe having an inner lining that provides sealing capabilities and structural reinforcement. Other methods that have been used for similar purposes include spray-on lining, grouting, and fold-and-form lining.
Many different resin systems are known to be acceptable for use in cured-in-place pipe lining and other applications for repairing underground structures. Most applications utilize thermoset resins. For instance, many known cured-in-place pipelining systems utilize epoxy, polyurethane, vinyl ester, or polyester resins. Thermoset resins are used for such applications for a variety of reasons, including the ease and flexibility of the lining process, the availability of a range of materials to provide substantial reinforcement within the existing pipe, and the relatively low cost of materials.
Thermoset resins may be formulated to cure under ambient conditions or under the application of heat. Both types of formulations have been used previously in cured-in-place pipelining applications. However, the use of such thermoset resins creates several problems during installation. The primary problem observed in the field is uncertain cure times due to ambient conditions. Since thermoset resins are generally formulated to cure in a specified time range under a set of specified environmental conditions, it is difficult to ensure that those conditions exist in the field. Even if the ranges of conditions that allow the resin to cure exist, there is still an uncertainty as to precisely how long the cure will take. This uncertainty leads to loss of production by an installer, inefficient use of labor and capital, and an increased risk of liner installation failure. These problems are exacerbated when using ambient cure resin systems, because an operator usually has no way of facilitating resin cure if ideal conditions are not met, such as by the application of additional heat. Therefore, there is a need in the art to address the deficiencies associated with the use of thermoset resin systems in cured-in-place pipe lining applications.